spurious(?) userland malloc/mmap failure

While running head r356494, my buildworld just failed due to an 
apparently spurious userland malloc/mmap failure.

===> usr.bin/finger (all)
objcopy: elf_update() failed: I/O error: Cannot allocate memory
--- all_subdir_usr.bin/finger ---
*** [all_subdir_usr.bin/finger] Error code 2

I ran 'make' in usr.bin/finger, and objcopy succeeded.  I then ran "make 
buildenv" followed by "make clean" and "make" in usr.bin/finger, which 
also worked.

buildworld was running with -j8, and a few C++ things were building 
concurrently, such as googletest and usr.bin/clang/llvm-objdump, so 
maybe the machine was under memory pressure.  It's a bhyve VM with 8 
CPUs and 8 GB RAM.

The full build log is:

https://people.freebsd.org/~vangyzen/2010-01-13-buildworld.txt

Eric